In general, electronic components are sealed with a resin material by a compression molding technique. In such compression molding, light-transmitting liquid resin such as silicone resin, for example, is employed. Thus, optical elements formed by LED (Light Emitting Diode) chips, for example, are sealed by compression molding.
In the compression molding, a compression molding apparatus shown in FIG. 18 is employed. This apparatus comprises a mold assembly 82 having an upper mold section 83, an intermediate mold section 84 and a lower mold section 85. In the compression molding employing this apparatus, light-transmitting liquid resin 87 such as silicone resin is supplied from a vertical dispenser 81 into a cavity 86 of mold assembly 82. Thus, a plurality of (e.g., eight) LED chips 89 mounted on a substrate 88 such as a lead frame are integrally sealed with resin by the compression molding.
The aforementioned compression molding method is now more specifically described.
First, vertical dispenser 81 is inserted between upper mold section 83 and lower mold section 85 of conventional mold assembly 82 for compression molding. At this time, lower mold section 85 is already covered with a mold releasing film 90. In this state, liquid resin 87 is dripped onto the middle position of cavity 86 of lower mold section 85 from a vertical nozzle 91 of vertical dispenser 81.
Then, lower mold section 85 and intermediate mold section 84 move toward upper mold section 83. At this time, substrate 88 is already set on upper mold section 83. Therefore, mold assembly 82 is closed while LED chips 89 mounted on substrate 88 are directed downward. Thus, LED chips 89 are immersed in liquid resin 87 stored in cavity 86.
After a lapse of a time necessary for curing liquid resin 87, mold assembly 82 is opened. Thus, the plurality of LED chips 89 are sealed in a resin molding corresponding to the shape of cavity 86. Consequently, a molding is completed. Thereafter the molding is cut along cutting plane lines. Thus, individual chip-type LEDs are completed.
While the aforementioned mold assembly 82 has the three-plate structure formed by upper mold section 83, intermediate mold section 84 and lower mold section 85, a mold assembly having a two-plate structure formed by an upper mold section and a lower mold section may also be employed.
However, the aforementioned conventional compression molding method disclosed in Japanese Patent Laying-Open No. 2003-165133, for example, leads to the following problems:    Patent Document 1: Japanese Patent Laying-Open No. 2003-165133 (refer to FIG. 2)